SAN FRANCISCO / House spider migrant setting up in Bay Area / Scientists ask public for help in studying how species adapts

Keay Davidson, Chronicle Science Writer

Published
4:00 am PST, Thursday, January 26, 2006

Mr. Darrell Ubick of the Californial Academy of Sciences and the Zoropsis spinimana, family Zoropidae is native to the Mediterranean and is now established in the San Francisco Bay Area.The California Academy of Sciences is studing the spider that makes no web for prey capture but runs down and kills its prey with speed and strength. .Photo by Lacy Atkins MANDATORY CREDIT FOR PHOTOG AND SF CHRONICLE/ -MAGS OUT less

Mr. Darrell Ubick of the Californial Academy of Sciences and the Zoropsis spinimana, family Zoropidae is native to the Mediterranean and is now established in the San Francisco Bay Area.The California Academy ... more

Photo: LACY ATKINS

Photo: LACY ATKINS

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Mr. Darrell Ubick of the Californial Academy of Sciences and the Zoropsis spinimana, family Zoropidae is native to the Mediterranean and is now established in the San Francisco Bay Area.The California Academy of Sciences is studing the spider that makes no web for prey capture but runs down and kills its prey with speed and strength. .Photo by Lacy Atkins MANDATORY CREDIT FOR PHOTOG AND SF CHRONICLE/ -MAGS OUT less

Mr. Darrell Ubick of the Californial Academy of Sciences and the Zoropsis spinimana, family Zoropidae is native to the Mediterranean and is now established in the San Francisco Bay Area.The California Academy ... more

Photo: LACY ATKINS

SAN FRANCISCO / House spider migrant setting up in Bay Area / Scientists ask public for help in studying how species adapts

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Bay Area scientists are asking local residents to keep an eye out for a relatively new resident of the south Bay Area -- a brownish spider with grayish spots that is up to 2 inches long when it stretches its legs.

Technically known as Zoropsis spinimana, the spider -- a native of the Mediterranean coastal countries and northern Africa -- somehow migrated to Northern California at an unknown time, perhaps by hiding inside someone's suitcase or inside a furniture shipment.

Zoropsis seems to be harmless: Calm and slow-moving, it didn't try bite or otherwise hurt Darrell Ubick, an expert at the California Academy of Sciences, who placed a member of the species on his arm.

Still, Ubick and his academy colleague, entomologist Charles Griswold, are asking Bay Area residents to watch for Zoropsis as part of a long-running research project to study how the spider species is settling down in the Bay Area.

They ask anyone who spots something that looks like Zoropsis around the house to avoid the temptation to squish it. Rather, let them know about the sighting by e-mailing a description of the creature to dubick@calacademy.org. A digital photo of the spider is even more helpful, Griswold said.

Such "exotic" (nonnative) species are fascinating partly because they can reveal how the local ecosystem is evolving over time as newcomers move in. Some exotic organisms threaten longer-established plant, insect or animal inhabitants.

At present there's, no known reason to suspect that Zoropsis threatens anybody or anything except the insects around your house, Ubick told The Chronicle.

"It's not harmful to us and it is a very attractive spider," said Ubick, an Academy arachnologist who first identified the newcomer in the early 1990s. He did so after a scientist at the U.S. Department of Agriculture asked him to help her classify a spider, originally found in San Jose, that she'd never seen before.

Indeed, Zoropsis is a pussycat, spiderwise: It comes from a long line of spiders that have grown accustomed to living inside human dwellings where the temperature is moderate and insects tend to congregate around food crumbs and other human-generated food supplies. Thus, Zoropsis needs humans to survive. "It can't compete with native species -- it wouldn't survive in the wild easily, but in the house it does just fine," Ubick explained.

Like a house cat? "Yes, exactly!" Ubick replied with a laugh.

With a chuckle, he advises anyone who really doesn't want the spider hanging around the house to "clean up your bread crumbs. That will reduce the number of insects and that, in turn, will reduce the number of spiders."

Unlike most spiders, Zoropsis doesn't bother erecting webs to capture its food. It's more of a nomadic diner that wanders around until it finds something to eat.

Over the past decade, most of the 40 to 50 Zoropsis sightings have occurred in the South Bay around San Jose and Santa Clara, but there have been a few scattered reports from Oakland -- as recently as last year -- and Redwood City.

So far, there have been no reported sightings of Zoropsis in San Francisco.

It's one of at least 40,000 known spider species in the world and roughly 1,500 in California, Ubick said. The first report of Zoropsis in scientific literature anywhere was in 1820 in Europe, when it was cited in a report by the 19th century spider expert Leon Dufour.

Although a 2-inch-long spider might sound big, especially to the spider-phobic, Zoropsis is puny compared with the Bay Area's biggest spiders. The Schwarzeneggers of Bay Area spiderdom are male tarantulas -- up to 5 inches wide -- that crawl around Mount Diablo and look for female tarantulas.

Spider at a glance

Scientific name: Zoropsis spinimana

Physical description: A large spider, up to three-quarters of an inch in body length and 1 1/2 to 2 inches long when legs are included. Its coloration is mostly dark brown, peppered with grayish spots on legs and abdomen. On the dorsal side of the abdomen, there is usually a dark pattern that flares outward two or three times before constricting to pointed end. Zoropsis spiders have eight eyes arranged in two rows of four, which gently curve toward the rear of the body. Zoropsis spiders look like wolf spiders but have much smaller eyes.

Range: Traditionally found in the circum-Mediterranean region of Europe. The first Bay Area specimen was discovered in San Jose and since then has spread slowly northward and can now be found in San Mateo, Alameda and Contra Costa counties.

Captive Zoropsis spiders do not appear to use webs to capture prey, instead they chase and pounce. The bite of this spider could easily pierce skin, although captive spiders did not appear to act aggressively. They are not considered dangerous.